The present invention relates to a process for preparation of nonionic surfactants wherein the molecular weight distribution of the nonionic surfactants obtained is in a narrow range.
The instant invention relates to the preparation of improved nonionic surfactant active agents and more particularly, to a process for the oxyalkylation of certain reactive hydrogen compounds to prepare nonionic surfactant active agents wherein the molecular weight distribution is narrow and wherein a novel magnesium-containing catalyst is employed to produce the nonionic surfactants.
Low molecular weight condensation products of an alkylene oxide, particularly ethylene oxide, or mixtures of alkylene oxides such as ethylene and propylene oxide with an alcohol are well known and for a long time have been prepared commercially for use in detergents, cleansing agents, dry cleaning materials, wetting and emulsifying agents and the like. These products are conventionally produced by reacting the reactive hydrogen compound with the alkylene oxide in the presence of a strongly alkaline or an acidic catalyst. Such preparative procedures result in the production of a mixture of relatively low molecular weight (up to about 2000) condensation product species containing a number of alcohol derivatives having different molecular proportions of alkoxylate. Thus, the reaction products generally obtained are, in reality, a mixture of derivatives of the alcohol moiety containing different molecular proportions of alkylene oxide units, i.e., having varying molar ratios of alcohol to alkylene oxide, and a wide range of molecular weights as well as having a certain proportion of unreacted alcohol. Moreover, as is well known, the conventional designation of the number of alkylene oxide units present per molecule of an alcohol alkoxylate is a designation of the average number of alkylene oxide units per molecule and that a substantial proportion of the alcohol alkoxylates present are present as alcohol alkoxylates having a greater and a lesser number of alkylene oxide units present than the actual average value would indicate. Such designations of such products is well understood in the art and will be employed herein consistent with is well understood meaning.
It is generally desirable to restrict, i.e. control the breath of the molecular weight distribution of the mixture to adjacent analogues of the desired product insofar as possible, since, as is well known, the number of moles of alkylene oxide in the reaction product is a major factor in determining what the properties of such products are, but as a matter of course it is quite difficult to control the molecular weight distribution. Acidic catalysts tend to give a narrower molecular distribution than alkaline catalysts, but, unfortunately, also contribute to the formation of undesired by-products. Thus, alkaline catalysts which are typically a strong base such as alkali metal hydroxides and alcoholates are generally used as the more efficient type of oxyalkylation catalyst, but the molecular distribution of the products are more diffuse, containing a greater proportion of lower and higher molecular weight species and smaller amounts of the species with the desired number of moles of alkylene oxide per mole of alcohol. For example, an 8-mole ethylene oxide (EO) adduct per mole of 1-dodecanol will contain not only the 8-mole EO adduct specie but also lower mole adducts and higher mole adducts. Lower mole adducts in the product mixture will range down to the one-mole adduct and higher adducts will extend up to 14 or 15 and beyond. The molecular weight ditribution is a measure of the relative amounts of the various adducts in the product mixture and can be represented in the form of a generally bell-shaped curve where the amount of each adduct species is plotted versus the number of moles of epoxide in the specie or of a description of the relative amount of each individual adduct. When the molecular weight distribution is characterized by a bell-shaped curve, a narrower distribution gives a sharper curve which is, higher at the middle and lower at the ends. A broader distribution curve would be lower at the middle portion of the range and higher at the ends, and such is not desirable.
Heretofore, several methods have been suggested for providing reaction products of an active hydrogen compound, e.g., alcohol, and epoxides which have a narrower range of molecular weights and molecular distribution of the epoxide units, and/or which reduce or eliminate the production of undesirable poly(alkylene glycol) and cyclic and straight chain ether by-products. For example, in U.S. Pat. No. 4,112,231 to Weibull et al it is disclosed that the use of certain neutral inorganic fluoborate and perchlorate salts will catalyze the reaction of epoxides with active hydrogen compounds to give products having a relatively narrower molecular distribution, i.e., a more limited range of molecular species and a larger proportion of desire molecular species; in U.S. Pat. No. 3,682,849 to Smith et al improved ethoxylated derivatives in C.sub.11 -C.sub.18 alcohols are prepared by removing unreacted alcohol and lower ethoxylates from the ethoxylate mixture prepared by conventional methods by use of vapor phase separation techniques; in U.S. Pat. No. 2,870,220 to Carter, a two-stage process is disclosed for preparing monoalkyl ethers of ethylene glycol and polyethylene glycols of more restricted molecular weight range wherein an alkanol and ethylene oxide is reacted in the presence of an acidic catalyst during the first stage and then in the second-stage after removal of acid catalyst and unreacted alkanol, reacting the mixture with ethylene oxide in the presence of an alkali metal alcoholate of the initial alkanol; and in U.S. Pat. No. 3,972,948 to Laemmle et al there is disclosed a method of preparing mono- and polyglycol ethers substantially free of undesired alkylene glycol by-products which method involves heating a reaction mixture containing an alkylene oxide and an alcohol in the presence of a catalyst containing alkali or alkaline earth cations wherein some or all of the catalyst is an anhydrous high boiling liquid residue prepared by concentrating the liquid residue from the same or different etherification processes after removal of the glycol ether product from the reaction mixture. None of the above-described processes and special catalysts disclosed in the art, however, are completely satisfactory in preparing a product with a desired molecular distribution in that such generally require multi-stage procedures or special acid-resistant equipment, may form undesirable by-products or simply do not provide sufficient control over the molecular weight distribution to be of a satisfactory nature. Thus, it would be highly desirable to develop a process where in the reaction of an alkylene oxide (epoxide) with an alcohol could be more readily carried out to prepare surfactant products that have a relatively narrower molecular weight distribution of analogue species and contain only small amounts, at most, of undesirable poly(alkylene glycol) and ether by-products.
Several patents are concerned with the preparation and advantages of nonionic surfactant products having a narrower molecular weight distribution. For example, U.S. Pat. No. 4,239,917 to Yang discloses the use of a class of basic barium materials as catalysts in the preparation of reaction products of alcohols and ethylene oxide so as to provide a product with a narrow, high mole adduct distribution while providing relatively low levels of undesirable by-products and unreacted free alcohol. The molecular weight distribution factor of the products produced during the oxyalkylation reaction is discussed at length by patentee and the differences in the molecular weight distribution of reaction products prepared with conventional alkali metal catalysts such as sodium hydroxide and those prepared using a barium catalyst of the invention is shown by graphical representations. The patent, to Yang, also shows that other alkaline earth metal materials, such as calcium hydroxide, magnesium oxide, and strontium hydroxide, were ineffective as catalysts for the oxyalkylation reaction. Thus patentee demonstrates that significant differences exist in catalytic effectiveness even between the various alkaline earth metals and not only between the barium catalysts of the invention and alkali metal hydroxides.
Further, U.S. Pat. Nos. 4,210,764 and 4,223,164 to Yang et al are concerned with the problem of the molecular weight distribution of products prepared by oxyalkylation of alcohols using conventional alkaline catalysts and are directed to overcoming an induction period problem frequently observed when employing barium-containing catalysts, such as those disclosed in U.S. Pat. No. 4,239,917. The patentees suggest the use of various phenols for use as a promoter for the barium-containing catalyst to overcome the induction period difficulty, and U.S. Pat. No. 4,223,164, disclose that with such promoters certain basic strontium materials may also be employed as a catalyst for the oxyalkylation reaction.
U.S. Pat. No. 4,453,022 describes the process for preparing nonionic surfactants containing a narrow molecular weight distribution by the use of a catalytic amount of a basic salt of calcium and/or strontium selected from the group consisting of hydroxide, alkoxide and phenoxide and a catalytic amount of an oxyalkylation catalyst promoter.
U.S. Pat. No. 4,721,817 describes alkylene oxide adducts of higher alkanols characterized by relatively narrow range distribution of alkylene oxide adducts by the use of a catalytically effective amount of a catalyst which combines one or more phosphorus-containing acids with one or more aluminum compounds selected from the group consisting of aluminum alcoholates and aluminum phenolates.
European Patent App. No. 0,082,569 shows alkanol soluble basic compounds of magnesium (which could include magnesium alkoxide) activated by alcohol ethoxylate.
It is believed that the instant invention provides an improved method for making narrow range oxyalkylation products using a novel catalyst containing magnesium and phosphorus.